The present invention relates to the activation of red mud formed in the Bayer alumina producing process and the utilization of activated red mud as adsorbent, catalyst, ion-exchanging substance and clarifying substance, particularly with respect to the catalytic cracking, adsorpting, decolorizing and clarifying processes.
It is well known that process for activating red mud from the Bayer process by baking an intimate mixture of red mud and of a caustic soda lye, at a temperature lower than 600.degree. C, then crushing and lixivating the product with hot water is disclosed in U.S. Pat. No. 2,432,071. This process needs so a great amount of caustic soda and heat energy that the cost of the operation is high, though the recovery of alumina of the vanadic acid of the red mud is taken into account. The activated red mud performed by said process is employing in adsorpting H.sub.2 S gas only. The mechanism of soda lye baking red mud is due to contains hydrated iron sesquioxide formed through the hydrolysis of a ferrite produced during baking.
Now I have discovered a economical wet process that is possible to make the Bayer red mud active as concerns adsorbent, catalyst, clarifying material and ion-exchanging material by submitting it to the following treatment;
Digest red mud and disperse the metal oxide compound particles in the compound of metal hydroxides and silica gel which comprises;
A. digesting the red mud with acid selected from the group consisting of HCl, H.sub.2 SO.sub.4, HNO.sub.3, H.sub.2 SO.sub.3, H.sub.2 CO.sub.3 and HF, PA1 b. adjusting the pH of the acid digested mixture comprising the sludge product to above 4 to precipitate the dissolved iron and aluminum as hydroxides along with silica gel on the surface of residual particles of red mud, PA1 C. separating the washing the gelation product, and PA1 D. heat treating the resulting active compound under 800.degree. C;
said method being further characterized in that the product of step (c) is treated comprising the process of shape making, prior to treatment in accordance with the next succeeding step.
The chemicals needed for activating red mud of the present invention are acid what is only, practically, in need of a reaction quantity of sodium component of mud in stoichiometry, and alkali for pH adjusting. The sodium component may be recovered as salt and the alkali compound may be reused in process cyclically by treatment. So that the cost of the present invention's operation is a not unconsiderable extent and can be aply easily in industry.
The active mechanism of the product of present invention is mainly due to the porous structure what is caused by the dispersing metal oxide compound particles in the amorphous compound formed by metal hydroxides and silica gel.
To employ the mud sludge, directly, from the sedimenter of alumina producing process in wet state without any pretreatment is one of the advantages of present invention.